The present invention relates to a valve operating mechanism for internal-combustion engines and has a valve and a pressure spring which seeks to move the valve into an end portion, the operating mechanism being supposed on a spring plate molted on an area of the valve which is adjacent to the valve shaft end.
As shown in German Patent Document DE-41 38 985 A1, the friction between a bucket tappet and a camshaft influences the mechanical efficiency ad therefore also the fuel consumption of an internal-combustion engine. This influence rises with an increasing number of valves per cylinder, which is illustrated in German Patent Document DE-40 39 256 A1. In this document, a spring plate is shown which consists of a ferrous-metal material and has a conical hub pan surrounding the valve shaft as well as a supporting part for the pressure spring which extends transversely with respect to the valve shaft. The hub part as well as the supporting part are dimensioned such that, when a ferrous-metal material is used for this spring plate, the occurring forces will be absorbed.
It is a object of the present invention to optimize a valve operating mechanism of an internal-combustion engine in the direction of its mechanical efficiency. However, in this case, special attention is to be paid to components of the valve operating mechanism, such as spring plates, which, because of their constructive structuring, are particularly suitable for a further development.
This and other objects are achieved by the present invention which provides a valve operating mechanism for internal-combustion engines comprising a valve having a valve shaft end, a spring plate mounted on an area of the valve which is adjacent to the valve shaft end, and a pressure spring supported on the spring plate ad providing a force on the valve towards an end position. At least the valve, the pressure spring and the spring plate are optimized with respect to their weights to thereby reduce valve operating masses.
Some of the principal advantages achieved by the invention are that the moved masses of the valve operating mechanism are reduced with the goal of decreasing the spring forces of the pressure spring and therefore the friction between the camshaft and the bucket tappet. As a result, the mechanical efficiency as well as the fuel consumption are improved. A component which can be optimized in a relatively simple manner with respect to moved masses is the spring plate which rests adjacent to the free end of the valve shaft, particularly, if it is made of a plastic material, preferably of a fiberglass-reinforced type. In order to achieve, in the case of such a selection of material, approximately the same conditions with respect to the stability, as they exist in the case of a conventional steel-spring plate, tensions must be reduced or the bendings of the supporting part must be maintained within defined limits. It is also important to avoid accumulations of material so that the "spring plate made of plastic" end product will be free of bubbles. Finally, the centering function of the spring plate for the pressure spring must also be taken into account.
According to the invention, the first widening of the cross-section on the hub part and the second widening of the cross-section on the supporting part as well as their constructive design are suitable for this purpose. In order to take into account the stress factors of the spring plate during the operation of the internal-combustion engine with respect to the temperature (180.degree. to 200.degree. C.), to engine oil (plus additives), to fuel, to water, to combustion residues and to exhaust gases, it is recommended that the following plastic materials be taken into consideration for the selection of materials: polyphthalamide, polyamide 46 (polytetramethylene adipidic-acid amide), phenolformaldehyde, or the like. Finally, injection molding process, casting processes or pressing processes are suitable for the manufacturing.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawings.